Derivatives

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#1
Hi can anyone advice on this question? I believe the gradient f is the same as y, therefore the derivative would be

Df/dx= 3rootx/2 + 15/2root x

Df/dx=9
And so sub in.

I don’t see what I am doing wrong.

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1 month ago
#2
You see how root is equal to a 1/2 you do x^3/2 because 1/2 x 3 is 3/2 and then the 15 root x is them same as 15x^1/2. Then differentiate and then set dy/dx to 9. U should get ur solutions
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1 month ago
#3
Hi I think I sort of understand your question but not fully so i just solved the question. I've attached a picture, hope it helps!!.
when you sub in both values of x in to gradient function, it gives you 9 so those are the values of x.
1
1 month ago
#4
(Original post by iman olam)
Hi I think I sort of understand your question but not fully so i just solved the question. I've attached a picture, hope it helps!!.
when you sub in both values of x in to gradient function, it gives you 9 so those are the values of x.
There was no need to square both sides could have just subbed in u=x^1/2.
1
1 month ago
#5
(Original post by tej3141)
There was no need to square both sides could have just subbed in u=x^1/2.
yeah, I'm well aware of that method but I'm just used this method which probably doesn't make sense because it's sort of longer but yeah.
Thanks though.
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#6
(Original post by iman olam)
Hi I think I sort of understand your question but not fully so i just solved the question. I've attached a picture, hope it helps!!.
when you sub in both values of x in to gradient function, it gives you 9 so those are the values of x.
Oh you legend.
No wonder I messed up! Haha what a tool.

I initially did square to remove the sqaure root but stupidly I didn’t expand properly and totally missed out the 45/2.

Thank you for this
1
1 month ago
#7
Always welcome🙂
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#8
(Original post by Flxmz)
You see how root is equal to a 1/2 you do x^3/2 because 1/2 x 3 is 3/2 and then the 15 root x is them same as 15x^1/2. Then differentiate and then set dy/dx to 9. U should get ur solutions
That’s just rearranging the function above in accordance to power rules. I derived the function above originally from what your suggesting as that’s the derivative of the original function I attached.
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